Drawing lubricant coating methods and compositions



Dec. 27, 1960 A. M. FUCINARI ET AL 2,966,425

DRAWING LUBRICANT COATING METHODS AND COMPOSITIONS Filed Feb. 18, 1959 2 Sheets-Sheet 1 INVENTORS ANGELO M. FUCINARI BY EDWARD L. KING M q Wm mm mm m A A A K A A W KUUV b A B kvw ATTORNEYS Dec. 27, 1960 A. M. FUCINARI ET AL 2,966,425

DRAWING LUBRICANT COATING METHODS AND COMPOSITIONS Filed Feb. 18, 1959 2 Sheets-Sheet 2 Fig.4-

INVENTORS ANGELO M. FUCINARI By EDWARD L.KING

ATTORNEYS United States Patent DRAWING LUBRICANT COATING METHODS AND COMPOSITIONS Angelo M. Fucinari, Detroit, and Edward L. King, Warren, Mich., assignors to The H. A. Montgomery Company, Detroit, Mich., a corporation of Michigan Filed Feb. 18, 1959, Ser. No. 794,166 12 Claims. (Cl. 117-49) This invention relates to improved metal working lubricants, and new methods of forming coatings of such lubricants on sheet metal. More particularly, the invention relates to so-called dry lubricant coatings and methods of forming them on metal surfaces to provide lubrication during subsequent metal working operations.

The principal objects of the present invention are to provide an improved dry lubricant coating on metal surfaces through the use of cleaning and coating solutions which do not have to be held at an elevated temperature during application; to apply the coating composition to the metal surface and to dry the coatings quickly and with a minimum of equipment occupying a minimum of floor space; to make use of existing conventional equipment for cleaning and coating the metal surfaces in accordance with the invention; to provide dry lubricant coatings on metal surfaces which will dry quickly and be effective throughout all stages of a multiple stage drawing operation; to provide lubricant coatings which will not build-up in the draw dies to cause interference in the fabrication of the metal, such as imprint damage; and to provide improved lubricant compositions especially adapted to achieve the foregoing other objects of the invention.

The advantages flowing from the invention are of particular importance in highly automated production lines in which metal sheets or continuous metal strips are moved substantially continuously at high speed from a suply point along a production line through cleaning, coating, drying, and single-stage or multiple-stage metal drawing machines. In such production lines, the floor space required for each operation is often a critical factor determining the cost and practicality of the operation. Also, whenever a new process is under consideration, the extent to which existing conventional equipment can be utilized is an important economic consideration.

As explained more fully hereinafter, the present invention meets the needs of industry in both of these respects by utilizing a minimum linear distance along a production line and by making it practical to use much of the existing equipment in plants formerly practicing prior coating processes. In addition, the present invention eliminates various costly laboratory control requirements of prior processes while producing superior lubricant coatings; and by applying the cleaning and coating compositions with rotating brushes and rollers, the cleaning and coating operations of the invention avoid dripping of these compositions around the applying machines and avoid the resulting diflicult housekeeping conditions that characterize various prior processes. A consequent further advantage is that efficient use of both the cleaning and coating compositions is realized. Also, the process and the cleaning and coating compositions are of such a non congealing character that the process may be closed down for any length of time and started up again with no expenditure of time either to prepare for shutting down or to prepare for resuming operation. The entire'cleaning, coating, and drying operations fit admirably into highly automated production lines in accordance with the current trends in all major manufacturing industries.

Metal-drawing lubricants are generally classified into two groups commonly referred to as wet lubricants and dry lubricants. Both types are applied as liquids, the Wet lubricant remaining liquid, but the dry lubricant being dried to form a solid film. The dry lubricant compositions are commonly applied as hot liquids, either as heated solutions or as hot melts depending upon the particular components therein.

The wet lubricants have been more widely used since a minimum amount of floor space and equipment is required for the application of the coating compositions. These lubricants usually are applied by spraying, manual swabbing, or with a roller. Spraying is not completely satisfactory since there is a great deal of waste due to over-spraying and loss of vapor to the surrounding atmosphere. As a rule, only about one-third of the sprayed material actually is retained on the surface of the metal. Manual swabbing or brushing requires the employment of additional manpower for the application of the coating composition and, therefore, is considered undesirable. Application of the coating composition by coating with a roller provides the most eflicient utilization of the coating material. However, roller coating generally cannot be employed with wet lubricants in multiple-stage drawing operations since the Wet lubricant must be reapplied after each drawing stage, and there is insufficient space to permit roller coating between stages, quite apart from the fact that the metal is no longer flat after the first draw and hence is difiicult to roller coat. Reapplication of coatings after each draw, therefore, must generally be either by swabbing or spraying.

To permit roller coating in multiple-stage drawing operations, it has been proposed to employ dry lubricants. Generally, one application of a dry lubricant is suificient for all of the drawing stages, and no lubricant need be added between stages. However, the use of dry lubricants creates a number of new problems.

The application of a dry lubricant to a metal surface requires, in addition to the coating step, a drying step and, in many cases, also a precleaning step. The precleaning step is necessary since dry lubricant coatings do not satisfactorily adhere to the metal surfaces unless the surfaces to be coated are substantially free of oil and other similar contaminants. This cleaning operation generally is accomplished by spraying a hot alkali solution onto the metal surface while brushing or otherwise scrubbing the surface. Although the hot alkali solution successfully removes the contaminants from the metal, any alkaline solution remaining on the metal surface after the treatment severely reduces the lubricity of the subsequently applied lubricant film. Thus, it is necessary to wash the metal surface with water to remove any traces of the alkaline cleaning solution before the coating composition is applied. The equipment necessary to perform the alkali precleaning operation occupies a substantial amount of floor space (for example, a space approximately 8 to 10 feet in length and wider than the metal sheets). The large amount of floor space required by the cleaning equipment and by the coating and drying equipment is a deterrent to the application of dry lubricant coatings in continuous metal drawing production lines.

Since the effectiveness of conventional dry lubricant films is dependent upon the degree of dehydration of the film, the lubricity of the film increasing as the amount of residual water decreases, it is necessary to remove substantially all of the water from the film. The removal of water from prior dry coatings, however, has been difficult since the .coating compositions have a marked tendency to congeal as they 6001 from the elevated temperatures at which they are applied. In congealing, a substantial amount of water is trapped in the film and removal thereof requires drying at relatively high temperatures and/or for long periods of time. This same tendency of the dry coating solutions to congeal as they cool requires troublesome control of temperatures of the solutions while in use and draining and cleaning of the solutions from the applying machines prior to shutdowns at the end of a day or over holidays and week ends.

In high temperature drying of the applied dry coating solutions, the metal is necessarily also heated. However, if the metal becomes too hot, workmen are not able to handle it efliciently even with special protection against the heat. Moreover, before fabrication of the metal can be started, the metal should be allowed time to cool, since the fabrication of hot metal causes the build-up of excess heat in the metal working tools or dies, resulting in excessive wear. The necessity for a metal cooling step makes a continuous coating and drawing process impractical in many plant operations. Another difliculty arises if the metal has been passed through a roller-leveler machine to remove age-hardening prior to coating, since any long delay at elevated temperatures before fabrication, e.g., a period of the order of eight hours or so, will result in a loss in the beneficial effects of the roller leveling step. Thus, close supervision and control of the process must be maintained to insure suflicient cooling of the metal while making sure that fabrication is completed before agehardening of the metal becomes significant.

From the above discussion, it will be apparent that, although satisfactory lubricant coatings for particular drawing operations could be obtained heretofore, the prior coating compositions were quite inflexible as regards the conditions under which they could be used and the methods by which they could be applied, and the prior methods of application were quite inflexible as regards their adaptability to different kinds of metal fabricating operations. In particular, none of the prior coating systems has been easily adaptable for general use in continuous, high speed, highly automated production line operations.

By employing the methods and compositions of the present invention, a number of specific important advantages are realized. The cleaning operation is simplified, the need for removing the cleaning solution is eliminated, and more thorough drying is rapidly accomplished. As a result, the method and compositions of the present invention enable the cleaning, coating, and drying operations to be completed within a much smaller floor space areathan was previously required. This reduction in floor space facilitates incorporation of these steps into a continuous coating and drawing production line.

In addition, a number of unexpected advantages arerealized from the present invention. The equipmentpreferably employed to accomplish the cleaning and coating steps is of a much lower cost, and much of the equipment used in prior processes and therefore, available in many plants, may be used with little or no change. Since both the cleaning and coating compositions can be easily and simply applied to metal surfaces without the compositions having been previously heated to elevated temperatures, no preparation time is required to heat these compositions before starting operation; and since the solutions do not congeal upon standing, theymay be left in the machine during a shutdown. Furthermore, the greater ease and speed of drying of the applied coating facilitate more complete water removal at lower temperatures and produce more effective lubricant filmswithout causing any significant heating of the metal itself. As a result, the metal cooling step formerly required after the application and drying of dry lubricant compositions is completely eliminated. In

addition, the lubricant-coated metal sheets of the present invention can be stored in stacks or rolls for extended periods of time, up to three months or so if desired, without deterioration of the coating or corrosion of the metal. Another advantage is the absence of coating build-up in the dies during fabrication, which buildup results in imprint damage on the surface of the metal.

In addition to all of the above advantages, the methods and compositions of the present invention possess a high degree of flexibility as regards the processes and apparatus that may be used for the formation of the lubricant coatings on metal surfaces. This flexibility greatly facilitates adaptation of the invention to varying production line setups, even where there are severely limiting conditions as regards the space that is available, the kinds of existing cleaning, coating, and/ or drying equipment that are available for use, the requirements of the subsequent metal forming operations, and the like.

In accordance with the present invention, metal sheets are prepared for subsequent fabricating operations by a process which comprises applying onto a surface of the sheet with pressure from a roller applicator surface a film of an aqueous coating composition which is liquid at ambient temperatures so as to force the film into intimate contact with the surface of the sheet, and evaporating water from said film until the moisture content thereof is reduced to less than about 15% by weight. The temperature of the coating composition and the metal sheet at all times is maintained below about 150 F.

The coating compositions employed in the process of the present invention are non-congealing, aqueous soap solutions comprising mixtures of an organic amine soap and an alkali metal soap, the soaps being formed with low titer fatty acids.

The soaps used in accordance with the present invention may be prepared using conventional soap-forming fatty acids having titers below about 30 C. These fatty acids may be mixtures of fatty acids derived from various oils, such as vegetable oils. For example, the acid mixtures derived from castor, coconut, palm kernel, linseed, olive, peanut, rape seed, corn, and soya bean oils are suitable. Also suitable are individual acids, such as oleic acid, ricinoleic acid, etc., which have been separated from fatty acid mixtures such as those mentioned above. In addition, fatty acids such as tall oil, which are formed as by-products of other reactions, also may be used.

The amines which are reacted with the low titer fatty acids to form the amine soaps may be any of the Watersoluble organic amines having boiling points above about C., for example, ethylene diamine, monoethanolamine, diethanolamine, triethanolamine, dimethyl ethanolamine, monoisopropanolamine, morpholine, and Z-aminol-butanol. Particularly advantageous for use in high speed roller coating processes which the amine soap is made with amines such as 2- amino 2 methyl 1 propanol; 2 amino 2 methyl- 1,3-propanediol; and 2-amino-2-ethyl-1,3-propanediol.

The alkali metal soaps of the present invention may be any of the conventional sodium and/or potassium derivatives of the low titer acids.

The selection of a particular coating composition formulation is primarily dependent upon the fabricating operation'which is subsequently to be performed on the metal, the deciding factor being the magnitude of the coetficient of friction between the work pieces and the tools. A method for evaluating this lubricant property is described in an article entitled Sliding Friction Test for- Metalworking Lubricants" by W. I. Wojtowicz, published in the May and June, 1955, issues of Lubrication Engineering.

As a'general rule, in the cold drawing of heavy gauge metal, it'is important that the lubricant coating provide are coating compositions in maximum protection against scoring. In such cases, it is advantageous to employ a coating composition in which the proportion of alkali soap is relatively great. As the thickness of the metal decreases below about 0.060 inch (16 gauge), scoring becomes of secondary importance, and softer coatings such as those containing a high proportion of the amine soap may be utilized. Soft coatings are generally preferred where applicable because of their high degree of mobility and high film strength.

The following formulations 1, 2, and 3 are examples of coating compositions which will produce films suitable for heavy gauge metal, Whereas formulations 4, 5, 6, and 7 produce softer films suitable for lighter gauge metal:

(1) Percent Triethanolamine 2.6 Caustic potash 3.7 Oleic acid 23.7 Water 70.0

Monoisopropanolamine 1.5 Caustic potash 3.7 Oleic acid 24.8 Water 70.0 2-amino-2methyl-l-propanol 1.8 Caustic potash 3.7 Castor fatty acids 24.5 Water 70.0

Triethanolamine 5.0 Caustic soda 1.8 Tall oil 23.2 Water V 70.0 Monoethanolamine 2.8 Caustic potash 2.5 Coconut fatty acids 24.7 Water 70.0 Monoisopropanolamine 4.7 Caustic soda 0.9 Corn fatty acids 24.4 Water 70.0 2-amino-2-methyl-l-propanol 5.3 Caustic soda 0.9 Soya bean fatty acids 23.8 Water 70.0

The proportion of the alkali metal soap to the amine soap may be varied over a considerable range from approximately one part of the alkali metal soap to three of the amine soap up to approximately three parts of the alkali soap to one of the amine soap. In other words, the alkali metal soap may comprise between about 25% and 75% by weight of the total soap with the amine soap comprising the remaining 75 to 25%.

Although the above formulations each contain 70% water, the water content may be varied in actual operations over a Wide range with amounts between about 5 0% and 95% by weight being generally employed, and amounts between about 70% and 90 or 95% being preferred. Changes in the proportion of water provide a simple and convenient means for controlling the film thickness in cases where film thickness is important. To facilitate shipping and storage of the coating compositions of the invention, more concentrated solutions containing less than about 50% water may be prepared and subsequently diluted before use. Surprisingly, even when the percentage of water is reduced to as low as 30% or so, there is generally no tendency for the compositions disclosed herein to congeal. ,This characteristic permits greater flexibility in the selection of the specific formulation and coating method to be employed,

The proportion. of water may be important when certain amine soaps are used. For example, when triethanol- 6 amine soaps are employed in the coating composition, there is an intermediate range of concentrations around 50% at which the composition becomes stiff, though it does not form a gel and thins out again at lower concentrations.

The coatings of the invention also may be modified by the incorporation of other materials in the coating compositions. For example, softer films may be produced by the incorporation of about 5% up to 10 or 15 of a suitable plasticizer. Among the suitable plasticizers are the water-soluble glycols and polyoxyethylene derivatives as well as the sulfonated or sulfated fatty oils.

Where the coated sheets are to be stacked for a period of time prior to fabrication, it may be desirable, in some cases, to incorporate an anti-blocking agent in the composition to minimize the sticking of one sheet to another. Suitable anti-blocking agents are those which are compatible with the coating compositions but which migrate to the surface of the coating to form a tack-free super,- ficial film upon removal of moisture. For example, methyl cellulose and/or polyvinyl alcohol, when used in amounts by weight of from 5 to 15% (anhydrous basis), minimize the blocking of coated metal.

The coating compositions of the present invention also may be modified, if desired, with small amounts of other materials which are known to improve the drawing qualities of lubricants, for example, water-insoluble materials such as chlorinated oils, flowers of sulfur, colloidal graphite, etc.

Although the coating compositions of the invention are particularly adapted for use in the roller coating process of the invention, the coating compositions also provide certain advantages when employed in other methods of coating, such as spraying or dipping. The viscosity of the coating composition will vary depending upon the particular coating method employed. For example, the coating compositions used in the roller coating process of the invention may have viscosities in the range of about 20 to 200 centipoises at 70 F., while for dip coating the viscosity may be as high as about 1000' centipoises at 70 F., and for spray coating might ap proach 5000 centipoises at 70 F.

The dry lubricant coatings produced on metal sheets by the employment of the coating compositions of the present invention are water-soluble, thermoplastic films having a wax-like texture. In addition, the coatings are substantially free of inorganic salts which permit'the coated metal to be welded without removal of the lubricant, whereas in the case of soap-borax dry lubricant coatings employed heretofore, it is necessary to remove the coating before welding. The lubricant films of the present invention have melting points in the range of about ISO-300 F. as determined using the Dropping Point of Lubricating Grease Test Method, ASTM D566-42. They have hardnesses in the range of about 40 to as determined by the Test for Needle Penetration of Petroleum Waxes, ASTM D1321-55T.

Another advantage of the roller coating process of the invention is the fact that the metal sheets do not have to be thoroughly clean when the coating composition is applied thereto. This is in direct contrast to the dry lubricant coating processes employed heretofore, in which it was necessary not only to thoroughly clean the sheets prior to coating, but also to make sure that any cleaning agent on the sheets was removed.

In accordance with the process of the invention, if the surface of the metal contains large amounts of oil and/or other contaminants, the metal sheet should be cleaned to remove at least the excess of the oil and other contaminants before the application of the coating composition. However, it has been found that when only a relatively thin film of oil is present or is left on the metal surface, the application of a coating composition of theinvention by roller coating without removing the oil film provides,

an adherent lubricant film on the metal. As the rolls apply the coating composition to the metal surface, the rollsbreak through the oil film and mix the oil into the coating composition. The coating composition, in turn, takes up the oil and makes it an integral part of the coating so that the oil will not interfere with the adhesion of the coating to the sheet.

The cleaning solution employed may be any one of the common metal cleaners, such as the aqueous or emulsion type cleaners. The cleaning solution, for example, may be an aqueous solution of one or more inorganic salts, such as the alkali carbonates or phosphates. Advantageously, a cleaning solution is selected which may be used without being heated so as to minimize any tendency toward reformation of age-hardening characteristics in the metal.

One of the important factors in selecting a cleaning solution is its ability to take up oils without emulsification of the oils in the solution. This characteristic permits easy separation of the oils from the cleaning solution so that the cleaning solution may be reused without purification merely by the addition of small quantities of water to replace any lost by evaporation. Generally, the oils and light dirt particles collected by the cleaning solution form a layer on the surface of the solution in the tank or reservoir in which the solution is stored. This permits the oils and light particles to be separated readily, e.g., by centrifuging, decanting, etc. Any heavy dirt particles settle to the bottom of the tank and may be removed periodically as needed.

The cleaning of the surfaces of metal sheets can be easily accomplished in conventional equipment already generally employed in connection with drawing operations. For example, the cleaning operation may be performed on a roller-leveler machine which is used to remove age-hardening characteristics by flexing metal sheets as they pass through the machine. This machine contains a pair of offset scrubbing brushes mounted one above and one below the path of the metal sheet near the entrance end of the machine, and a spray of the cleaning solution may be applied to both the top and bottom surfaces of the metal sheet at the point of contact between each brush and the sheet. In place of a roller-leveler machine, any apparatus containing similar scrubbing brushes and at least one pair of driving rollers may be employed.

To insure that the lubricant coating on the metal sheet is uniform and adherent, it is important that any nonuniform accumulations of cleaning solution on the sheet, such as puddles, be removed prior to the coating step. This may be accomplished by the use of rubber squeegee rolls at the exit of the scrubbing machine, by blowing a blast of air against the surface of the sheet as it emerges from the scrubber, or by a combination of these steps. It is not necessary to remove all of the cleaning solution from the sheet, but it is important that the solution be uniformly distributed over the sheet.

As stated above, the coatingcomposition is applied to the surface of the metal sheet with suitable roller coating apparatus. Advantageously, the roller coater may be of a design similar to that described in US. Patent 2,774,684 to Fucinari. In this apparatus, a doctor roll is associated with each coating'roll, and the coating composition is distributed. on the coating roll by applying the composition at the juncture of the doctor and coating rolls. The pressure between the doctor and coating rolls determines the thickness of film applied to the metal sheet, and the thickness can be controlled by changing the pressure.

The thickness of the film applied to the metal sheet may be varied over a considerable range, depending upon the particular drawing operations to be performed. For example, satisfactory thicknesses for most fabricating operations will v'ary from about 0.00004 to about 0.0003 inch thickness corresponding to coating weights of between'about 100 and700 milligrams per square foot of surfacei One of the unexpected advantages of the coating process of the present invention is the complete flexibility in the starting-up and shutting-down of the equipment. In the dry lubricant coating processes employed heretofore, it was necessary to drain the coating machines or else keep the machines heated even during relatively short shut-down periods to prevent the coating compositions from congealing in the apparatus. Moreover, if the coating machine was accidentally or intentionally permitted to cool and the lubricant coating composition congealed, it was then necessary to begin reheating the machine well before resumption of the coating operation. In contrast, the coating compositions of the present invention may be applied at ambient temperatures, e.g., in the range of about 50 to F., and, since they are non-congealing in character, the process may be closed down for any length of time and started again with no expenditure of time or expense to prepare for shutting down the process or to prepare for resumption of operations.

After the film is applied to the metal sheet, the excess water therein is evaporated from the coating. The water may be removed merely by air-drying at room temperature or with moderate heat in a variety of ways, depending upon space limitations, speed of travel of the metal sheet, and the importance of limiting the tem perature of the metal. Since the coating compositions of the present invention are non-congealing, the excess moisture in the applied coating can be removed relatively quickly merely by circulating air over the surface of the coated metal sheet at room temperature or at moderately elevated temperatures. By contrast, the dry lubricants employed heretofore quickly congealed and formed an impervious skin on the surface of the coating, making the removal of additional quantities of water difficult and the employment of relatively high temperatures and/or a long drying time essential.

One of the unexpected advantages of the lubricant coatings of the present invention is that they possess a high degree of lubricity even when as much as about 10% to 15% by weight of water remains in the coating. As a result, the removal of water from the coatings is, advantageously, only continued until the moisture content of the coating is reduced to about 5 to 10%. This is in direct contrast to the previously known' dry lubricants, which required substantially complete dehydration of the coating. This was because the lubricity of the coatings was reduced severely even when amounts of moisture as low as 5% by weight remained in the coatings. The retention of about 5 to 10% moisture in the coatings produced in accordance with the present invention, however, helps in maintaining the lubricity characteristics of the film at a high level and assists in the prevention of lubricant build-up on the draw dies.

When heat is employed to assist in the drying of the film, it is important that the amount of heat be controlled so that the temperature of the metal sheet will not exceed about 150 F. Advantageously, the temperature of the metal is kept below about F. Since the metal is not permitted to absorb any significant amount of heat, the drawing operation can be performed as soon as the excess water has been removed without causing the draw dies to overheat. Overheating may cause press control problems and may lead to scoring and even breakage, of the draw parts. In addition, difficulties in the handling by workers of metal which is too hot are not encountered, and reformation of agehardening characteristics in the metal is minimized.

As stated above, the method of the present invention may be successfully carried out even under severely limiting conditions as regards the available floor space and equipment which may be utilized. For example, where the amount of space is limited and only a conventional roller-leveler machine is available, the complete coating operation may be carried out on the rollerleveler itself. In this case, the coating solution may be the present invention will be described more particularly with reference to the. accompanying drawings, in which Figs. 1, 2, 3, and 4 schematically show four different illustrative apparatus arrangements suitable for use in accordance with the invention.

Referring first to Fig. 1, a sheet of steel 11 from a stack of sheets on a hydraulically adjustable table 12 may be cleaned by passing it through a conventional roller-leveler machine 13 having a pair of offset scrubbing brushes 14 followed by a series of straightening rolls 16. As the steel sheet 11 passes between each of the scrubbing brushes and a guide roller 15, a cleaning solution is applied to both sides of the sheet by means of pipes equipped with series of spray heads or nozzles 17 directed into the juncture between each brush and the metal sheet. Oil and other contaminants are removed from the metal sheet 11 by the combined action of the cleaning solution and scrubbing brushes 14. Excess cleaning solution dripping or thrown from the brushes, the rollers, and the metal sheet itself may be trapped in the housing of the machine and controlled by any suitable arrangement of baflles (not shown) for downward flow into a collection and supply reservoir 18 from which the supply of solution to the spray heads 17 may be pumped for recirculation.

As mentioned above, oil and light particles removed from the metal sheet 11 will accumulate on the surface of the solution in the reservoir 18 and can be drained off, as desired, for example, by maintaining the level of the solution in the reservoir 18 substantially constant and continuously flowing the upper portion of the body of liquid down through an overflow pipe 19 to suitable separating apparatus (not shown). Heavy dirt particles, metal slivers, etc., will slowly accumulate in the bottom of the reservoir 18 and require removal only at infrequent intervals.

The cleaned sheet 11 then passes through the series of straightening rolls 16, which remove the age-hardening characteristics from the sheet preliminary to drawing. The sheet 11 emerging from the roller-leveler 13 then passes beneath nozzle 20, which directs a blast of air against the top surface of the sheet to blow off any excess cleaning solution that may have accumulated in the form of puddles, leaving a thin liquid film of the cleaning solution uniformly distributed over the surface. The cleaning solution removed is collected in trough 20a, which extends laterally to each side of the sheet 11 for this purpose. Rollers 20b merely support the sheet above the trough 20a.

The sheet 11 then passes through a roller coating apparatus 21 having a pair of vertically aligned rubber rolls 22 for applying the coating compositions to the cleaned steel sheet. The coating composition is applied to the rubber coating rolls 22 in the machine 21 by pipes 23, which flow the coating composition between converging surfaces of each rubber roll 22 and an associated steel doctor roll 24. Advantageously, the coating rolls and the doctor rolls are of about the same size, for example, about five to eight inches in diameter. The pressure of each doctor roll 24 against its associated rubber coating roll 22 controls the thickness of the film applied to the coating roll, and the pressure of the pair of opposed coating rolls 22 on the steel sheet 11 controls the amount of the films that are transferred onto opposite sides of the steel sheet. The thickness of the deposited film also de pends upon the physical characteristics of the rubber cover on the coating roll. Generally, a rubber cover at least about three-fourths inch thick and having a durometer hardness in the range of about 25 to S5 is preferred.

After being coated, the steel sheet 11 is passed through a drying apparatus 25 to dry the film. The sheet may be carried through the drier on a foraminous belt 26 of steel mesh construction, or the like, which permits air to pass therethrough. The film is dried by circulating hot air on both sides of the sheet, as by means of one or more blowers 27 and bafiles 28 and 29 appropriately located above and below the steel sheet. The temperature of the air and length of the drier 25 are selected relative to the conditions of the coated sheets 11 so that, when they emerge from the drier, the coating preferably contains about 5 to 10% moisture, and the temperature of the sheet itself is not above about F. The coated sheets 11 may then pass directly to any desired metal working equipment or may be stacked for storage.

The apparatus of Fig. l is an assembly of largely conventional machines that are available in many metal working plants and can be adapted with little or no modification for cooperative use in carrying out the present invention. Such apparatus has the advantage, for proper situations, of making maximum use of existing equipment in converting a plant from a prior type of coating operation to one embodying the present invention.

Referring next to Fig. 2 of the drawing, a schematically illustrated scrubbing machine of simpler design is shown which may be substituted for the modified roller-leveler machine 13 in the assembly of Fig. 1. Such a substitution would be desirable where no existing roller-leveler machine is available and the removal of age-hardening char acteristics is unnecessary.

The scrubbing machine of Fig. 2, generally designated 13a, may comprise a casing 31 housing a first pair of driving rolls 32, a pair of offset scrubbing brushes 33, and second and third pairs of driving rolls 34 and 35, between which the same steel sheets 11 may be passed. The rolls and brushes rotate in the directions shown by the arrows in the drawing. The same cleaning solution used in the apparatus of Fig. 1 may be employed and may be applied in the same manner from spray heads 36, supplied with cleaning solution from a reservoir 37 in the bottom of the machine. As in Fig. l, the reservoir may have an overflow pipe 38 through which a layer of oil and light dirt from the sheet 11, accumulating on top of the body of cleaning solution, may be drawn 011. Where even greater compactness is desired in the direction of travel of a continuous steel sheet 11, the first pair of driving rolls 32 and the pair of driving rolls 34 may be omitted to reduce the length of the machine accordingly. Once the sheet 11 is forced between the driving rolls 35 beyond the brushes 33, the rolls 35 will effectively function to pull the sheet continuously through the scrubbing machine and feed it to a coating machine.

As a part of scrubbing machine 13a, a pair of rubber squeegee rolls 39 may be included to remove excess cleaning solution remaining on the metal sheet and leave a uniform liquid film of the cleaning solution.

Referring next to Fig. 3, a conventional rolIer-leveler machine and pair of simple fans are shown for performing the coating and drying operations (with no prior washing) where space limitations are particularly severe. Such a machine may be satisfactorily used for coating provided the starting metal sheets are relatively clean and only thin lubricant coatings are required.

The coating machine of Fig. 3, generally designated 40, may comprise a casing 41 housing the same arrange ment of scrubbing brushes 42, guide rollers 45, and leveling rollers 43 as the combination cleaning and rollerleveler. machine 13 of Fig. 1. The same steel sheets 11 may be passed through this machine in the same manner as through the machine 13 of Fig. 1. A coating solution may be applied to sheet 11 by brushes 42 which are .supplied by pipes equipped with spray heads or nozzles 44, as shown. As the coated sheet advances between leveling rollers 43, the coating is kneaded into contact with the surface of the sheet to provide a uniform, adherent coating.

Since the coatings applied through the use of the roller- Ileveler machine 40 are relatively thin coatings of around 100 mg. weight per square foot of steel surface, the coatings dry rapidly without heat and, at most, a blast of air from a pair of fans 46 is all that will normally be required to dry the coatings. As a result, the coated sheet may be passed directly to metal working machines for fabrication or to stacking equipment for storage.

Referring next to Fig. 4, still another arrangement of :apparatus is disclosed utilizing the scrubbing machine 13a of Fig. 2 and the coating machine 21 of Fig. 1 to :receive a continuous steel sheet 11a from a supply reel .50 and a conventional straightening machine 51. After emerging from the scrubbing machine 13a, the cleaned sheet is passed through a blast of air from a nozzle 20, similar to that shown in Fig. 1, to remove any excess -of cleaning solution which might tend to form puddles on the surface of the sheet. This air blow-off treatment supplements the wiping efiect achieved with squeegee rolls 39 positioned at the exit of scrubbing machine 13a. Thereafter, the sheet is coated in coating machine 21, land, as the sheet emerges from the coating machine, it is turned back on itself and fed under the coating machine 21, scrubbing machine 13a, straightening machine 51, and reel 50 to provide a distance of travel of the coated sheet during which the coating may be dried, with or without using a forced air draft or moderate heat to aid the drying. In this manner, the length of the equipment for scrubbing, coating, and drying may be minimized while providing a relatively long drying path. After the drying step, the coated sheet may be passed directly to metal working machines for fabrication, or to cutting or re-rolling equipment for preparing the coated steel for storage in stacks or in rolls.

'From the foregoing description of several machine assemblies for carrying out the present invention, it will be appreciated that the invention is highly flexible as regards the apparatus required to accomplish the various objectives and advantages of the invention. The cleaning and coating solutions used in accordance with the invention may be employed without change in the several illustrative cleaning and coating machine assemblies for performing the essential process steps of the invention as described herein.

From the above description, it will also be apparent to one skilled in the art that many additional modifications of the invention may be made while accomplishing some or all of the various objects and advantages of the invention described herein. Therefore, the invention as defined by the appended claims is intended to cover all such modifications and equivalents of the illustrative details shown and described.

What is claimed is:

l. A process of preparing a sheet of metal for subsequent fabrication, which comprises applying and forcibly pressing into intimate contact with a surface of the sheet a film of a noncongealing, aqueous soap solution which is liquid at ambient temperatures and which contains at least about by weight of soap, and evaporating water from said film until the moisture content thereof is reduced to less than about 15% by weight while maintaining the temperature of said soap solution and said ma :1 sheet at all times below about 150 F.

2. A process of preparing a sheet of metal for subsequent fabrication, which comprises applying and forcibly pressing into intimate contact with a surface of the sheet a film of a noncongealing, aqueous soap solution which is liquid at the application temperature and which contains at least about 5% by weight of soap, and evaporating water from said film until the moisture content thereof is reduced to less than about 15% by weight while maintaining the temperature of said film and said metal sheet at the completion of the evaporating step below about F.

3. A process of preparing a sheet of metal for subsequent fabrication, which comprises applying and forcibly pressing into intimate contact with a surface of the sheet a film of a noncongealing, aqueous soap solution which is liquid at ambient temperatures and which contains at least about 5% by weight of soap, and evaporating water from said film until the moisture content thereof is reduced to between about 5% and 15% by weight while maintaining the temperature of said soap solution and said metal sheet at all times below about 150 F.

4. A process of preparing for subsequent fabrication a sheet of metal having a coating of oil thereon, which comprises removing at least a part of the oil from said sheet, applying and forcibly pressing into intimate contact with a surface of said sheet a film of a noncongealing, aqueous soap solution which is liquid at ambient temperatures and which contains at least about 5% by weight of soap, and evaporating water from said film until the moisture content thereof is reduced to less than about 15 by weight while maintaining the temperature of said soap solution and said metal sheet at all times below about 150 F.

5. A process of preparing a sheet of metal for subsequent fabrication, which comprises applying and forcibly pressing into intimate contact with a surface of the sheet a film of a noncongealing, aqueous soap solution which is liquid at the application temperature and which contains at least about 5% by weight of soap, and heating said film to evaporate water therefrom until the moisture content is reduced to less than about 15% by weight while maintaining the temperature of said film and said metal sheet at the completion of the evaporating step below about 150 F.

6. A process of preparing for subsequent fabrication a sheet of metal having a coating of oil thereon, which comprises cleaning said sheet with a cleaning solution to remove at least a part of the oil, removing any nonuniform accumulation of cleaning solution from said sheet, applying and forcibly pressing into intimate contact with a surface of said sheet a film of a noncongealing, aqueous soap solution which is liquid at the application temperature, and which contains at least about 5% by weight of soap, and evaporating water from said film until the moisture content thereof is reduced to between about 5% and 15% by weight while maintaining the temperature of said film and said metal sheet at the completion of the evaporating step below about 150 7. A process of preparing for subsequent fabrication a sheet of metal having a coating of oil thereon, which comprises applying a cleaning solution to said sheet, scrubbing said sheet to remove at least a part of the oil, removing any non-uniform accumulation of cleaning solution from said sheet, applying and forcibly pressing into intimate contact with a surface of said sheet a film of a noncongealing, aqueous soap solution which is liquid at ambient temperatures and which contains at least about 5% by weight of soap, and evaporating water from said film until the moisture content thereof is reduced to less than about 15% by weight while maintaining the temperature of said soap solution and said metal sheet at all times below about 150 F., said cleaning solution and said soap solution being substantially at ambient temperatures when applied to said sheet.

8. A process of preparing for subsequent fabrication a sheet of metal having a coating of oil thereon, which comprises applying a cleaning solution to said sheet, scrubbing said sheet to remove at least a part of the oil, removing any non-uniform accumulation of cleaning solution from saidsheet, applying and forcibly pressing into intimate contact with a surface of said sheet a film of a noncongealing, aqueous soap solution which is liquid at ambient temperatures and which contains at least about by weight of soap, and heating said film to evaporate water therefrom until the moisture content thereof is reduced to less than about 15% by weight while maintaining the temperature of said soap solution and said metal sheet at all times below about 150 F., said cleaning solution and said soap solution being substantially at ambient temperatures when applied to said sheet.

9. A process of preparing for subsequent fabrication a sheet of metal having a coating of oil thereon, which comprises applying a cleaning solution to said sheet, scrubbing said sheet to remove at least a part of the oil, removing any non-uniform accumulation of cleaning solution from said sheet, applying and forcibly pressing into intimate contact with a surface of said sheet a film of a noncongealing, aqueous soap solution which is liquid at ambient temperatures and which contains at least about 5% by weight of soap, and heating said film to evapd rate water therefrom until the moisture content thereof is reduced to between about 5% and 15% by weight while maintaining the temperature of said soap solution and said metal sheet at all times below about 150 F., said cleaning solution and said soap solution being substantially at ambient temperatures when applied to said sheet.

10. A process of preparing a sheet of metal for subsequent fabrication, which comprises applying onto a surface of the sheet with pressure from a rolling applicator surface a film of an aqueous coating composition which is liquid at ambient temperatures so as to force said film into intimate contact with the surface of said sheet, and evaporating water from said film until the moisture content thereof is reduced to less than about 15% by weight while maintaining the temperature of said coating composition and said metal sheet at all times below about 150 F., said coating composition comprising a non-congealing liquid, aqueous soap solution in which the soap comprises a mixture of an amine soap and an alkali metal soap which have been formed from low titer fatty acids, the proportion of water in said solution being suificient to prevent gelation of the solution at ambient temperatures and sufiicient to maintain the viscosity of the solution between about 20 and 200 centipoises at 70 F.

11. A process of preparing for subsequent fabrication a sheet of metal having a coating of oil thereon, which comprises applying a cleaning solution to said sheet, scrubbing said sheet to remove at least a part of the oil, removing any non-uniform accumulation of cleaning solution from said sheet, applying onto a surface of said sheet with pressure from a rolling applicator surface a film of an aqueous coating composition which is liquid at ambient temperatures so as to force said film into intimate contact with the surface of said sheet, and evaporating water from said film until the moisture content thereof is reduced to less than about 15% by weight while maintaining the temperature of said coating composition and said metal sheet at all times below about 150 F., said cleaning solution and said coating composition being substantially at ambient temperatures when applied to said sheet, and said coating composition comprising a non-congealing, liquid, aqueous soap solution in which the soap comprises a mixture of an amine soap and an alkali soap which have been formed from low titer fatty acids, the proportion of water in said aqueous solution being between about 50% and by weight, said amine soap being formed from a water-soluble organic amine having a boiling point above about C., and said amine soap comprising between about 25% and 75% by weight of the total soap.

12. A process of preparing for subsequent fabrication a sheet of metal having a coating of oil thereon, which comprises applying a cleaning solution to said sheet, scrubbing said sheet to remove at least a part of the oil, removing any non-uniform accumulation of cleaning solution from said sheet, applying onto a surface of said sheet with pressure from a rolling applicator surface a film of an aqueous coating composition which is liquid at ambient temperatures so as to force said film into intimate contact with the surface of said sheet, and heating said film to evaporate water therefrom until the moisture content thereof is reduced to between about 5% and 15 by weight while maintaining the temperature of said coating composition and said metal sheet at all times below about F., said cleaning solution and said coating composition being substantially at ambient temperatures when applied to said sheet, and said coating composition comprising a non-congealing, liquid, aqueous soap solution in which the soap comprises a mixture of an amine soap and an alkali soap which have been formed from fatty acids having a titer below about 30 C., the proportion of water in said aqueous solution being between about 70% and 90% by weight, said amine soap comprising between about 25% and 75% by weight of the total soap, and said amine soap being formed from a water-soluble organic amine selected from the group consisting of Z-amino-Z-methyl-l-propanol, 2-amino-2- methyl-1,3-propanediol, and 2-amino-2-ethyl-1,3-propanediol.

References Cited in the file of this patent UNITED STATES PATENTS 10,482 Pomeroy May 31, 1854 1,129,304 Loudenbeck Feb. 23, 1915 1,833,899 Hoyt Dec. 1, 1931 2,067,530 Ihrig Jan. 12, 1937 2,144,642 Stoughton et a1 Jan. 24, 1939 2,199,627 French et a1 May 7, 1940 2,216,376 Rimmel Oct. 1, 1940 2,428,364 Frager Oct. 7, 1947 2,430,400 Hoelscher Nov. 4, 1947 2,565,938 Williams Aug. 28, 1951 2,631,978 Bersworth Mar. 17, 1953 2,662,836 Montgomery Dec. 15, 1953 2,686,732 Montgomery Aug. 17, 1954 2,774,684 Fucinari Dec. 18, 1956 2,776,918 Bersworth Jan. 8, 1957 2,785,078 Keating et al Mar. 12, 1957 2,849,107 Logue Aug. 26, 1958 2,850,418 Otto Sept. 2, 1958 2,861,955 Aylesworth Nov. 25, 1958 2,871,140 6055 Jan. 27, 1959 

1. A PROCESS OF PREPARING A SHEET FOR SUBSEQUENT FABRICATION, WHICH COMPRISES APPLYING AND FORCIBLY PRESSING INTO INTIMATE CONTACT WITH A SURFACE OF THE SHEET A FILM OF NONCONGEALING, AQUEOUS SOAP SOLUTION WHICH IS LIQUID AT AMBIENT TEMPERATURES AND WHICH CONTAINS AT LEAST ABOUT 5% BY WEIGHT OF SOAP, AND EVAPORATING WATER FROM SAID FILM UNTIL THE MOISTURE CONTENT THEREOF IS REDUCED TO LESS THAN ABOUT 15% BY WEIGHT WHILE MAINTAINING THE TEMPERATURE OF SAID SOAP SOLUTION AND SAID METAL SHEET AT ALL TIMES BELOW ABOUT 150*F. 